Cell therapeutics has been recently spotlighted as a new field of intractable disease treatment. Organ transplantation, gene therapy, or the like has been proposed before for the intractable disease treatment. However, due to immune rejection, short supply of organs, and lack of knowledge about vector development or pathological genes, such organ transplantation or gene therapy was not effectively put into practical use.
As an interest in cell therapeutics is on the rise, a transplant technique using in vitro proliferation of cells that are separated from a living body has been commercialized. In addition, artificial skin or reconstruction of cartilage or fibrous tissue has been put into practical use. Fibroblasts are cells that produce and maintain interstitial extracellular matrix (ECM), and fibroblasts are organically connected by ECM. In addition, fibroblasts are well known as cells that produce a variety of cytokines and physiologically active factors in terms of immune defense.
To utilize such fibroblasts as a cell therapeutic agent or a tissue engineering material, fibroblasts have been cultured two-dimensionally for mass proliferation, and then, treated with an enzyme, such as trypsin. However, in resulting fibroblasts, ECM produced therefrom was degraded so that the role of the ECM was not able to be expected at the transplantation stage. Meanwhile, studies have been carried out to culture various cells including fibroblasts into a three-dimensional (3D) cell cluster by using an artificial 3D porous ECM, called a scaffold that is fabricated by using a natural polymer or a biodegradable synthetic polymer, according to an engineering technique. However, due to limitations of materials in terms of a biodegradation rate or an inflammation reaction, it has difficulties in commercialization of a 3D cell cluster. Thus, a technique for inducing formation of a 3D cell cluster is required.
Skin tissue of the human body can be divided into three parts: epidermis which is the outermost skin layer; dermis which is a skin layer below epidermis; and hypodermis (or subcutaneous tissue). Among these parts, epidermis consists of epithelial cells and other melanin cells and immune cells, wherein the epithelial cells are differentiated into several layers from a basement membrane that is configured to firmly bind epidermis with dermis. Here, dermis under epidermis mainly consists of fibroblasts and several extracellular matrices secreted by the fibroblasts. Dermis is also known to be closely related to skin health and aging.
Collagen is a major protein that accounts for 90% of dermis, and is configured to maintain skin connective tissue and provide skin elasticity. In general, the number and function of fibroblasts decrease in accordance with external factors and aging, and such decreased number and function of fibroblasts are known to be the main cause of skin aging. The decrease in the number of cells reduces synthesis of fibrous components in skin tissue and causes loss of water and changes in stratum corneum. In addition, the increase in collagenase reduces cross-linked collagen, thereby reducing smoothness, moisture, and elasticity of the skin. The increased content and synthesis of collagen mean increased moisture and elasticity of the skin.
The degradation and synthesis of collagen in the skin matrix are controlled by a protease, for example, matrix metalloproteinase (MMP). Depending on a structure and functional characteristics, MMP is divided into various types. Type I collagen which is typical collagen in the skin is degraded by the action of MMP-1. The activity of MMP-1 is controlled by an inhibitor, such as TIMP-1 that is secreted to maintain skin homeostasis. Here, biomolecules, such as MMPs and TIMPs, are secreted by cells including fibroblasts. In addition, MMP-1 degrades extracellular matrix, thereby promoting tumor metastasis and progression. The synthesis and degradation of collagen by MMP-1 play an important role in cancer metastasis. Thus, a drug or substance targeting MMP-1/collagen is being developed to be utilized as a cancer therapeutic agent or a cosmetic composition.
In addition, MMP is known to be overexpressed in pathological conditions, such as an inflammatory disease including arthritis, or cancer including cancer metastasis, so that an MMP inhibitor targeting MMP has been developed as a therapeutic agent for the diseases above.
In this regard, 2D cell-based assays for screening a drug targeting MMP or collagen have been developed. However, such 2D cell-based assays are limited due to drug sensitivity, drug penetration into cells and tissues, or the like, and are inadequate to accurately predict the response in living organisms. In addition, due to the structural and functional complexity of the skin, skin research using a single type of skin cells has limitations. A skin model having a 3D structure designed to overcome limitations uses artificial skin, but existing artificial skin is difficult to screen a drug at a high speed. Therefore, development of a new skin model system that can screen a drug at a high speed for high-throughput and mimic the skin environment is required.